Design And Biomechanical Investigation Of A Pre-stress Endosseous Implant Of Artificial Limbs

The modern acceptance cavity prosthetic technology has insurmountabledefects by itself. Negative pressure type connection between the stump andacceptance cavity generates special smell because of poor ventilation; the frictionof weight may lead stump to infection of ulceration; also the load-bearing way isunfit to the human biomechanics, and artificial limb would cause unpleasant gait.Osseointegrated prostheses is the new design which can be away from thetraditional acceptance cavity by passing strength of human physiological activityto the stump bone by the endosseous implant, the biomechanical characteristicsof which is very close to the nature state. However, mechanics compatibleproblem between bone and the implant, which lead to the failure of the implantby bone absorption in the use of long-term because of stress shielding yet to beresolved.Improving the material properties or the design of the endosseous implant,which make the stress distribution of the bone closer to the physiological state, to solve the problem of compatibility between the bone and the implant. Thus weprovide the design of pre-stress endosseous implant of artificial limbs, andevaluate the stability and the biomechanical of the new design.Referring to Pre-compression fixation technique of “Limb Salvage Implant”which is mature and used in clinical and relevant parameters of femoral marrowcavity morphology and femoral mechanics, designing and manufacturingStainless steel model of pre-stress endosseous implants of artificial limb; bychanging the pre-load value in the assembly process to find the minimumpre-pressure which can effective prevent the relative displacement betweenimplant and femoral; also by applying strain electrical measurement principlesand techniques, with normal femoral stress value as the reference, finding thedifference of stress shielding between Pre-press endosseous implants and theTraditional screw-type endosseous implants.The design of pre-stress endosseous implant of artificial limbs has obtainedthe patent for utility model. The study of stability shows that the implant will bestable after implanting as long as the pre-stress load is greater than1750N. Theresults of the strain electrical measurement show that the femoral stressdistribution is close to normal after the implantation of pre-stress endosseousimplant. Compared with screw-type prosthetic implant, highly significantdifference（p0.01）between the two implants was found at all measuring pointsexcept L4and M4.The result of the research suggest that the design of pre-stress endosseousimplant of artificial limbs is reasonable, it can make staging operation to oneoperation, meanwhile making sure the impant is stable. Comparing to thetraditional screw-type endosseous implants, it has better biomechanical properties,and can significantly reduces the stress shielding degree on the surrounding bone tissue to avoid the stress sheltering effect occurred. These research providesgrounds to the clinic research, development and application of theOsseointegrated prostheses.